1. Field of the Invention
This invention generally relates to a denture for either a maxilla (upper jaw) or a mandible (lower jaw), and more particularly, to a manufacturing method of a denture having uneven patterns on a surface for contact with a mucous membrane (hereinafter called a mucosa-fronted surface). This invention also relates to a refractory model for preparing a metal denture having uneven patterns on its mucosa-fronted surface, and its manufacturing method. This invention further relates to a working model used to prepare a denture of a dental resin having uneven patterns on its mucosa-fronted surface, and a manufacturing method of the working model.
2. Discussion of the Related Art
Dentures involving maxillary and mandibular dentures are prepared based on a positive model of a patient""s oral cavity. Mucosa-fronted part of the base of a denture for contact with a mucous membrane, including a gingival surface or gum, is made by using a dental resin or metal. In the pertinent field of industry, dentures are generally classified into metal dentures or dental resin dentures, depending on their materials. When making a denture, a dental technician normally prepares a negative model from a positive model (which may be a direct master model or a replica of the master model). Then, in case of preparing a metal denture, the technician first prepares a refractory model, and next makes a metal base using an appropriate metal material by a known method. In case of preparing a dental resin denture, the technician first prepares a working model from a negative model, and next makes a resin base using an appropriate dental resin material by a known method.
Regarding metal dentures, in recent movements of dental materials from traditional materials like gold and platinum to other metals excellent in biocompatibility, such as Ti alloy, Coxe2x80x94Cr alloy and Mg alloy, for example, metal dentures made using known techniques such as precision casting and lost wax process have been brought into practice. See for example, xe2x80x9cShika Giko Kogaku Rinsho Kenshu Koza 5 (Prosthodontia Clinical Workshop Vol. 5), pp. 121-162, published by Ishiyaku Shuppan Kabushiki Kaisha (Medical, Dental and Pharmaceutical Publication Company). A process of preparing such a metal denture generally includes, for example: preparing a positive model (which is either a master model as a direct replica of a patient""s oral cavity or a replica of the master model); imparting the pertinent surface of the positive model (positive surface) onto an impression material such as plaster, agar, silicone, or the like; and next making a copy model (refractory model) by using the impression material after it has been imparted with the pertinent surface. It is empirically known that, in the case of metals having high fusing points, such as a Ti alloy and a Coxe2x80x94Cr alloy, if the texture of the shape-defining surfaces (hereinafter called shaping surfaces) of their molds are rough, problems such as bubbles, blowholes or voids are caused.
Typically, the mucosa-fronted surface of the part of a denture base (including the area for covering a gingival surface or gum) has minute irregularities that are copied from the configuration of the patient""s mucous tissues. If the patient""s mucous tissues are rough, for example, the shaping surface of a casting mold becomes a roughly irregular plane in the case of, for example a metal denture. Therefore, a denture base made by using the mold results in a still rougher plane on its mucosa-fronted surface due to bubbles produced during the casting process. This results in requiring a great deal of work in the final polishing process.
Taking those problems into account, the inventor proposed a casting method of a casting mold in his Japanese Patent Application No. 7(1995)-315299, laid open as Japanese Laid-Open Publication No. 9(1997)-155505 on Jun. 17, 1997. He also proposed the concept of, prior to taking or imparting the positive surface, i.e. the shaping surface, of a positive mold (master model or a replica of the master model) onto an impression material, putting a thin flexible film over the positive surface, and then bringing the flexible thin film into close contact with the positive surface under a suction force, and thereafter injecting the impression material.
In this novel method, the general contour of the shaping surface transferred to the impression material faithfully traces the positive model. Its surface texture, however, inherits the smooth surface texture of the flexible thin film. As a result, the resultant refractory model having the imprint of the shaping surface transferred from the impression material exhibits a smooth surface texture copied from the surface of the flexible thin film without any influences from the actual configuration of the patient""s mucous membrane. Thus it is possible to alleviate the problems of bubbles, blowholes and voids in the casting process and to attain improvements in the final polishing efficiency as well as a significant reduction in the number of defective products.
Having confirmed the excellent effects of that novel technique, the inventor performed further research to proceed with this technique, and has achieved the present invention.
It is therefore an object of the invention to provide a denture giving a user a feeling of a stable fitting, and a method for fabricating such a denture.
A further object of the invention is to provide a refractory model for preparing a metal denture that can give a user a feeling of a stable fitting, and a method for fabricating such a refractory model.
A still further object of the invention is to provide a working model for preparing a dental resin denture capable of giving a user a feeling of a stable fitting, and a method for fabricating such a working model.
According to the invention, there is provided a method for manufacturing a denture which includes a base having uneven patterns on a mucosa-fronted surface thereof for contact with a person""s mucous membrane, comprising the steps of:
providing a shaping surface of a master model or a negative model with a pattern model for making the uneven patterns;
covering the shaping surface bearing the pattern model for the uneven patterns thereon with a flexible thin film;
bringing the flexible thin film into close contact with the model; and
pouring a transfer material onto the flexible thin film in close contact with the model and curing the transfer material therein.
The term xe2x80x9cuneven patternsxe2x80x9d used in this application pertains to any arrangement of a plurality of intentionally embossed, debossed or engraved portions from the standard level forming a land or lands.
Usable as the copying material are plaster, agar, silicone and other known materials. However, plaster is preferably used.
The pattern model for the uneven patterns can be made by, for example, cutting a piece of an appropriate size out of a commercially available netting material, and putting it in contact with the shaping surface of the model. Alternatively, the pattern model for the uneven patterns may be made by selectively coating wax onto the shaping surface of the model. Alternatively, the pattern model of the uneven patterns may be made by bonding a plurality of thin pieces of an appropriate sheet material onto the shaping surface of the model.
These and other features and objects of the invention will become clearer in the light of the following detailed description of the preferred embodiments of the invention described later with reference to the attached drawings listed below.